var path = require('path');
var fs = require('fs');

function Mime() {
  // Map of extension -> mime type
  this.types = Object.create(null);

  // Map of mime type -> extension
  this.extensions = Object.create(null);
}

/**
* Define mimetype -> extension mappings. Each key is a mime-type that maps
* to an array of extensions associated with the type. The first extension is
* used as the default extension for the type.
*
* e.g. mime.define({'audio/ogg', ['oga', 'ogg', 'spx']});
*
* @param map (Object) type definitions
*/
Mime.prototype.define = function (map) {
  for (var type in map) {
    var exts = map[type];

    for (var i = 0; i < exts.length; i++) {
      this.types[exts[i]] = type;
    }

    // Default extension is the first one we encounter
    if (!this.extensions[type]) {
      this.extensions[type] = exts[0];
    }
  }
};

/**
* Load an Apache2-style ".types" file
*
* This may be called multiple times (it's expected). Where files declare
* overlapping types/extensions, the last file wins.
*
* @param file (String) path of file to load.
*/
Mime.prototype.load = function(file) {
  // Read file and split into lines
  var map = {},
      content = fs.readFileSync(file, 'ascii'),
      lines = content.split(/[\r\n]+/);

  lines.forEach(function(line) {
    // Clean up whitespace/comments, and split into fields
    var fields = line.replace(/\s*#.*|^\s*|\s*$/g, '').split(/\s+/);
    map[fields.shift()] = fields;
  });

  this.define(map);
};

/**
* Lookup a mime type based on extension
*/
Mime.prototype.lookup = function(path, fallback) {
  var ext = path.replace(/.*[\.\/]/, '').toLowerCase();

  return this.types[ext] || fallback || this.default_type;
};

/**
* Return file extension associated with a mime type
*/
Mime.prototype.extension = function(mimeType) {
  return this.extensions[mimeType];
};

// Default instance
var mime = new Mime();

// Load local copy of
// http://svn.apache.org/repos/asf/httpd/httpd/trunk/docs/conf/mime.types
mime.load(path.join(__dirname, 'types/mime.types'));

// Load additional types from node.js community
mime.load(path.join(__dirname, 'types/node.types'));

// Default type
mime.default_type = mime.lookup('bin');

//
// Additional API specific to the default instance
//

mime.Mime = Mime;

/**
* Lookup a charset based on mime type.
*/
mime.charsets = {
  lookup: function(mimeType, fallback) {
    // Assume text types are utf8
    return (/^text\//).test(mimeType) ? 'UTF-8' : fallback;
  }
}

module.exports = mime;